This invention relates to suspension systems and particularly to suspension systems for seats and sleeper bunks used in trucks. Although a seat suspension would normally provide no particular benefit in an automobile which can be designed to provide a soft, comfortable ride, it is quite desirable in trucks which conventionally have stiff suspensions to accommodate heavy loading conditions. Unfortunately, the rather substantial cost of suspension seats has generally limited their use to the driver's seat position on heavy trucks. As a result, passengers in the cabs of heavy trucks must endure a gret deal of physical discomfort. Light and medium duty trucks are generally equipped with bench type seats and fixed back cushions. When such vehicles are empty or only lightly loaded their occupants are subjected to a great deal of bouncing which causes their backs to rub up and down and slap the seat back cushion.
In an effort to increase passenger comfort, consideration has been given to mounting a bench seat on a suspension such as that shown in Simons et al U.S. Pat. No. 3,109,621. The result is less than completely satisfactory since one would either have to utilize a pair of complete suspensions, with their consequent cost and weight, under the ends of the bench, or the suspension and seat base would have to be made extremely rigid and heavy to carry the load from one side of the seat to the other.
U.S. Pat. No. 3,760,436 to Zach et al. shows a suspension for a sleeper bunk of a type usable in trucks where one occupant sleeps while the other drives. Since the unit incorporates a single pair of scissors link suspension members it will be obvious that the suspended platform would have to be made quite rigid and heavy if it was to be used as a wide seat support rather than as a mattress support. Christensen U.S. Pat. No. 3,882,558, shows a suspended sleeper bunk which comprises a bottom frame carrying a rotatable drum at each end. The drums support a mattress support platform hanging downwardly therefrom by means of flexible webs. Since the drums are connected for simultaneous rotation, the platform tends to remain level when loading is applied between the drums. However, loading applied beyond the drums would tend to lift the unsupported opposite end of the platform since the flexible webs can only resist downward loads. Thus, the system would not be suitable for suspending a wide seat which would be subject to downward loading at its ends and horizontal loading into the back of the seat.